CN112828928A

CN112828928A - Gear device and robot

Info

Publication number: CN112828928A
Application number: CN202011306090.9A
Authority: CN
Inventors: 片冈祐哉
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2019-11-22
Filing date: 2020-11-19
Publication date: 2021-05-25
Anticipated expiration: 2040-11-19
Also published as: US11536358B2; US20210156459A1; CN112828928B; JP2021081046A; JP7467893B2

Abstract

The present disclosure relates to a gear device and a robot, and provides a technology for smoothly rotating a wave generator of the gear device. The gear device includes an internal gear, a flexible external gear, and a wave generator. The wave generator has an elliptical shaped cam and bearing. The inner peripheral surface of the external gear is coated with grease. A groove is provided along the rotary shaft in at least one of the inner peripheral surface of the external gear and the outer peripheral surface of the bearing.

Description

Gear device and robot

Technical Field

The present disclosure relates to a gear device and a robot including the gear device.

Background

In a robot, a reduction gear is generally provided in a drive shaft of a motor in order to drive a joint portion of a robot arm. As such a reduction gear, for example, a gear device described in patent document 1 is known.

The gear device is provided with: an annular internally toothed gear; a flexible external gear partially meshing with the internal gear; and a wave generator that contacts an inner peripheral surface of the external gear and moves a meshing position of the internal gear and the external gear in a circumferential direction around the rotation axis. The wave generator has: a cam having an elliptical outer peripheral surface; and a bearing disposed between an inner peripheral surface of the external gear and an outer peripheral surface of the cam. The bearing is a deep groove ball bearing in which a plurality of balls are held between an inner ring and an outer ring. The outer gear has a grease reservoir on its inner peripheral surface, and the grease flows between the inner peripheral surface of the outer gear and the outer peripheral surface of the outer ring of the bearing and between the outer gear and the inner gear, and functions as a lubricant.

Patent document 1: japanese patent laid-open publication No. 2002-349681

However, the inventors of the present disclosure found the following problems: since the outer ring of the bearing of the wave generator rotates relative to the external gear with the rotation of the wave generator, it is difficult to maintain sufficient grease between the inner peripheral surface of the external gear and the outer peripheral surface of the outer ring of the bearing, and as a result, it is difficult for the wave generator to rotate smoothly.

Disclosure of Invention

According to a first aspect of the present disclosure, a gear device is provided. The gear device is provided with: an internal gear; an external gear having flexibility, the external gear partially meshing with the internal gear and relatively rotating around a rotation axis with respect to the internal gear; and a wave generator that contacts an inner peripheral surface of the external gear and moves a meshing position of the internal gear and the external gear in a circumferential direction around the rotation shaft. The wave generator has a cam having an outer peripheral surface with an elliptical shape, and a bearing disposed between the inner peripheral surface of the external gear and the outer peripheral surface of the cam. The inner peripheral surface of the external gear is coated with grease, and a groove is provided along the rotating shaft in at least one of the inner peripheral surface of the external gear and the outer peripheral surface of the bearing.

According to a second aspect of the present disclosure, a robot is provided. The robot includes: a first member constituting a base or an arm; a second member that constitutes an arm portion and is provided to be rotatable with respect to the first member; and a gear device that transmits a driving force from one side to the other side of the first member and the second member. The gear device is provided with: an internal gear; an external gear having flexibility, the external gear partially meshing with the internal gear and relatively rotating around a rotation axis with respect to the internal gear; and a wave generator that contacts an inner peripheral surface of the external gear and moves a meshing position of the internal gear and the external gear in a circumferential direction around the rotation shaft. The wave generator has a cam having an outer peripheral surface with an elliptical shape, and a bearing disposed between the inner peripheral surface of the external gear and the outer peripheral surface of the cam. The inner peripheral surface of the external gear is coated with grease, and a groove is provided along the rotating shaft in at least one of the inner peripheral surface of the external gear and the outer peripheral surface of the bearing.

Drawings

Fig. 1 is a diagram showing a schematic configuration of an embodiment of a robot according to the present disclosure.

Fig. 2 is an exploded perspective view illustrating a gear device according to an embodiment of the present disclosure.

Fig. 3 is a longitudinal sectional view of the gear device shown in fig. 2.

Fig. 4 is a front view of the gear arrangement shown in fig. 2.

Fig. 5 is an explanatory diagram showing an example of a groove formation between an inner peripheral surface of the external gear and an outer peripheral surface of the bearing.

Fig. 6 is an explanatory diagram showing another example of the groove formation of the inner peripheral surface of the external gear and the outer peripheral surface of the bearing.

Description of the reference numerals

1 … gear arrangement; 2 … internal tooth gear; 3 … external gear; 4 … wave generator; 23 … internal teeth; 31 … a body portion; 32 … bottom; 33 … external teeth; 35 … opening; a 41 … cam; 42 … bearing; 100 … robot; 110 … control devices; 111 … base; 120 … robot arm; 121 to 126 … arm parts; 130 … hands; 131. 132 … finger; 140 … force detector; 150 … electric motor; 311 … inner peripheral surface; 321. 322 … pore; 331 … first end; 332 … second end; 351 … slot; 411 … shaft portion; 412 … cam portion; 421 … inner ring; 422 … ball bearing; 423 … outer ring; 424 … outer circumferential surface; 431. 441 … orbital plane; 444 … outer peripheral surface; 451 … groove.

Detailed Description

Fig. 1 is a diagram showing a schematic configuration of an embodiment of a robot according to the present disclosure. The robot 100 shown in fig. 1 is a six-axis vertical articulated robot, and can perform operations such as feeding, discharging, conveying, and assembling of precision equipment and components constituting the precision equipment, for example.

The robot 100 includes a base 111, a robot arm 120 connected to the base 111, a force detector 140 provided at a distal end of the robot arm 120, and a hand 130. The robot 100 further includes a control device 110, and the control device 110 controls a plurality of drive sources that generate power for driving the robot arm 120. The drive source includes a motor 150 and a gear device 1.

The base 111 is a portion for mounting the robot 100 at an arbitrary installation site. The installation location of the base 111 is not particularly limited, and examples thereof include a floor, a wall, a ceiling, a movable cart, and the like.

The robot arm portion 120 includes a first arm portion 121, a second arm portion 122, a third arm portion 123, a fourth arm portion 124, a fifth arm portion 125, and a sixth arm portion 126, which are connected in this order from the base end side to the tip end side. The first arm portion 121 is connected to the base 111. An end effector such as a hand 130 for gripping various members is detachably attached to the distal end of the sixth arm 126. The hand 130 has two

fingers

131 and 132, and can grip various components and the like with the

fingers

131 and 132, for example.

The base 111 is provided with a drive source having a motor 150 such as a servo motor for driving the first arm portion 121 and a gear device 1 as a reduction gear. Although not shown, each of the arm portions 121 to 126 is also provided with a plurality of drive sources including motors and speed reducers. Each driving source is controlled by the control device 110.

In the robot 100, the gear device 1 transmits a driving force from one side to the other side of the base 111 as a first member and the first arm 121 as a second member. More specifically, the gear device 1 transmits a driving force for rotating the first arm portion 121 with respect to the base 111 from the base 111 side to the first arm portion 121 side. Here, the gear device 1 functions as a speed reducer, and thereby the first arm portion 121 can be rotated with respect to the base 111 while reducing the rotation of the driving force from the motor 150. It is noted that "rotation" includes movement in one direction or two directions including opposite directions with respect to a certain center point, and rotation with respect to a certain center point.

In this way, the robot 100 includes: a base 111 as a first member constituting the base; a first arm portion 121 as a second member constituting an arm portion provided rotatably on the base 111; and a gear device 1 that transmits a driving force from one side to the other side of the base 111 and the first arm 121.

Note that, of the second arm portion 122 to the sixth arm portion 126, any number of arm portions selected in order from the first arm portion 121 side may be used as the "second member". That is, it can be said that a structure including any number of arm portions selected in order from the first arm portion 121 side among the first arm portion 121 and the second to sixth arm portions 122 to 126 is a "second member". For example, the structure constituted by the first arm part 121 and the second arm part 122 may be referred to as a "second member", and the entire robot arm part 120 may be referred to as a "second member". Further, the "second part" may also include a hand 130. That is, the structure constituted by the robot arm 120 and the hand 130 may be said to be the "second member".

The robot 100 described above includes the gear device 1 described below. Hereinafter, the gear device 1 will be described as an example of the gear device of the present disclosure.

Fig. 2 is an exploded perspective view illustrating a gear device according to an embodiment of the present disclosure. Fig. 3 is a longitudinal sectional view of the gear device shown in fig. 2. Fig. 4 is a front view of the gear arrangement shown in fig. 2. In the drawings, the dimensions of the respective portions are exaggerated as necessary for convenience of explanation, and the dimension ratio between the portions does not necessarily coincide with the actual dimension ratio.

The gear device 1 shown in fig. 2 to 4 is a wave gear device, and is used as a speed reducer, for example. The gear device 1 includes: a rigid internally toothed gear 2; an external gear 3 having flexibility, the external gear 3 partially meshing with the internal gear 2 and relatively rotating around a rotation axis a with respect to the internal gear 2; and a wave generator 4 that contacts the inner peripheral surface of the external gear 3 and moves the position of engagement between the internal gear 2 and the external gear 3 in the circumferential direction around the rotation axis a. Although not shown, a lubricant such as grease is appropriately disposed as necessary in the sliding portion and the contact portion in the gear device 1. For example, the inner peripheral surface 311 of the external gear 3 is coated with grease and functions as a grease reservoir.

In the present embodiment, the internal gear 2 is fixed to the base 111 which is the first member of the robot 100, the external gear 3 is connected to the first arm 121 which is the second member of the robot 100, and the wave generator 4 is connected to the rotation shaft of the motor 150 of the robot 100.

When the rotation shaft of the motor 150 rotates, the wave generator 4 rotates at the same rotation speed as the motor 150. Since the internal gear 2 and the external gear 3 have different numbers of teeth, the meshing positions thereof move in the circumferential direction and rotate relatively around the axis a due to the difference in the numbers of teeth. The axis a is also referred to as "rotation axis a". In the present embodiment, the number of teeth of the internal gear 2 is larger than that of the external gear 3, and therefore the external gear 3 can be rotated at a rotation speed lower than that of the motor 150. That is, a reduction gear having the wave generator 4 as an input shaft side and the external gear 3 as an output shaft side can be realized.

Note that the connection form of the internal gear 2, the external gear 3, and the wave generator 4 is not limited to the above-described form, and for example, even if the external gear 3 is fixed to the base 111 and the internal gear 2 is connected to the first arm portion 121, the gear device 1 can be used as a speed reducer. In addition, even if the external gear 3 is connected to the rotation shaft of the motor 150, the gear device 1 can be used as a reduction gear, and in this case, the wave generator 4 may be fixed to the base 111 and the internal gear 2 may be connected to the first arm portion 121. When the gear device 1 is used as a speed-increasing gear, the relationship between the motor 150 as the input side and the first arm 121 as the output side may be reversed.

The structure of the gear device 1 will be briefly described below. As shown in fig. 2 to 4, the internal gear 2 is a gear made of a rigid body that does not substantially flex in the radial direction, and is an annular gear having internal teeth 23. In the present embodiment, the internal gear 2 is a spur gear. That is, the internal teeth 23 have a tooth trace parallel to the axis a. It is noted that the tooth trace of the internal teeth 23 may also be inclined with respect to the axis a. That is, the internal gear 2 may be a helical gear or a herringbone gear.

The external gear 3 is inserted inside the internal gear 2. The external gear 3 is a flexible gear that can flex and deform in the radial direction, and is an external gear having external teeth 33 that mesh with the internal teeth 23 of the internal gear 2. The number of teeth of the external gear 3 is smaller than that of the internal gear 2. In this way, the reduction gear can be realized by the difference in the number of teeth between the external gear 3 and the internal gear 2.

In the present embodiment, the external gear 3 is formed in a cup shape having an opening 35 at the left end in the axis a direction of fig. 3, and external teeth 33 are formed on the outer peripheral surface thereof. Here, the external gear 3 has a cylindrical barrel portion 31 around the axis a, and a bottom portion 32 connected to one end portion side of the barrel portion 31 in the direction of the axis a, that is, the right side in the direction of the axis a in fig. 3.

As shown in fig. 3, a hole 321 penetrating along the axis a and a plurality of holes 322 penetrating around the hole 321 are formed in the bottom portion 32 of the external gear 3. The hole 321 is through which a shaft body, not shown, on the output side can be inserted. The holes 322 can be used as screw holes through which screws for fixing the output-side shaft body to the bottom portion 32 are inserted. Note that these holes may be provided as appropriate or omitted.

As shown in fig. 3 and 4, the wave generator 4 is disposed inside the external gear 3 and is rotatable about an axis a. Then, the wave generator 4 deforms the cross section of the body portion 31 of the external gear 3 into an elliptical or oblong shape having the major axis La and the minor axis Lb, and causes the external teeth 33 to mesh with the internal teeth 23 of the internal gear 2. Here, the external gear 3 and the internal gear 2 are engaged with each other so as to be rotatable about the same axis a.

The external gear 3 has two

end portions

331, 332 in the direction along the axis a. Of the two

end portions

331 and 332, the end portion 331 on the opening 35 side is referred to as a "first end portion 331", and the end portion 332 on the opposite side of the first end portion 331 is referred to as a "second end portion 332". The main body 31 near the first end 331 is a portion where large deformation due to coning occurs. Coning refers to the following three-dimensional deformation: the body 31 is expanded outward with respect to the axis a on the major axis La side shown in fig. 4, and the body 31 is narrowed inward with respect to the axis a on the minor axis Lb.

The wave generator 4 has a cam 41 and a bearing 42 mounted on the outer periphery of the cam 41. The cam 41 has a shaft 411 rotating around the axis a and a cam portion 412 protruding outward from one end of the shaft 411. Here, the outer peripheral surface of the cam portion 412 is formed in an elliptical shape or an oval shape having the vertical direction in fig. 3 and 4 as the major axis La when viewed from the direction along the axis a. The bearing 42 includes a flexible inner ring 421 and an outer ring 423, and a plurality of balls 422 arranged therebetween.

Here, the inner ring 421 is fitted into the outer peripheral surface of the cam portion 412 of the cam 41, and is elastically deformed into an elliptical shape or an oval shape along the outer peripheral surface of the cam portion 412. Accordingly, the outer ring 423 is also elastically deformed into an elliptical or oblong shape. The outer peripheral surface 444 of the outer ring 423 abuts against the inner peripheral surface 311 of the body portion 31. The outer circumferential surface of the inner ring 421 and the inner circumferential surface of the outer ring 423 form track surfaces 431 and 441, respectively, which guide the plurality of balls 422 in the circumferential direction and roll the balls. These track surfaces 431 and 441 are formed into circular arcs having a cross section slightly larger in radius than the radius of the ball 422. The plurality of balls 422 are held by a holder, not shown, so that a circumferential distance therebetween is constant.

In the wave generator 4, as the cam 41 rotates about the axis a, the orientation of the cam portion 412 changes, and the outer ring 423 is deformed to move the meshing position between the internal gear 2 and the external gear 3 in the circumferential direction. Note that, at this time, the inner ring 421 is fixedly provided to the outer peripheral surface of the cam portion 412, and thus the deformation state is not changed.

Fig. 5 is an explanatory diagram showing an example of the groove formation of the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42 of the wave generator 4. Here, a partial cross section of the external gear 3 cut by a cut surface passing through the axis a is drawn. On the other hand, with respect to the wave generator 4, an appearance is depicted instead of a cross section. As described above, the grease GR is applied to the inner peripheral surface 311 of the external gear 3.

In this example, a groove 351 along the rotation axis a is provided on the inner peripheral surface 311 of the external gear 3. In addition, the groove 351 is provided in plural. These grooves 351 are also referred to as "first grooves 351". The phrase "groove 351 along rotation axis a" means that when a line segment parallel to rotation axis a is drawn on inner circumferential surface 311, the angle formed by the line segment and groove 351 is 30 degrees or less. By providing the groove 351, the grease GR can be easily held between the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42. The groove 351 also has a function of guiding the grease GR between the external gear 3 and the internal gear 2. In order to realize this function, the angle formed by the groove 351 and the rotation axis a is preferably 5 degrees or less, and particularly the groove 351 is preferably parallel to the rotation axis a. Further, a plurality of grooves 351 are preferably provided. Further, it is preferable that the plurality of grooves 351 extend parallel to each other.

In the example of fig. 5, the groove 351 extends from the first end 331 to the second end 332 of the external gear 3. The groove 351 is preferably provided over a portion R42 of the inner peripheral surface 311 of the external gear 3 that is in contact with the bearing 42 of the wave generator 4. According to this configuration, since the groove 351 is provided in the inner peripheral surface 311 of the external gear 3 over the portion R42 that contacts the bearing 42 of the wave generator 4, the grease GR can be easily held between the external gear 3 and the bearing 42 of the wave generator 4. Further, since the groove 351 extends from the first end portion 331 toward the second end portion 332 of the external gear 3 on the opening 35 side, the grease GR can be easily guided between the external gear 3 and the internal gear 2 via the first end portion 331. In the example of fig. 5, the groove 351 is formed from the first end 331 over a portion corresponding to the entire range of the external teeth 33 of the external gear 3. In this way, the grease GR can be easily kept sufficiently between the external gear 3 and the bearing 42 of the wave generator 4. Further, even if the portion R42 is assumed to move in the direction along the rotation axis a, the grease GR can be easily held between the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42.

The width and depth of the groove 351 are preferably set to appropriate dimensions corresponding to the dimensions of the solid additive contained in the grease GR. For example, when the size of the solid additive is 10 μm or less, it is preferable that the width of the groove 351 is at least 10 μm. The depth of the groove 351 is preferably smaller than the width, and is preferably half the width, for example. The reason why the depth of the groove 351 is made smaller than the width is that the solid additive has a depth of contact with both the external gear 3 and the bearing 42 of the wave generator 4, and therefore the retention of the grease GR can be improved. In addition, in consideration of the case where pressure is applied to the solid additive by the external gear 3 and the bearing 42 of the wave generator 4, the depth of the groove 351 is preferably made smaller than the width. As the grease GR, for example, a grease using an organic molybdenum as a solid additive and a lithium soap base as a thickener can be used. When the depth of the groove 351 is too small, the function of holding the grease GR is not exhibited, and therefore, the depth of the groove 351 is preferably 5 μm or more, more preferably 10 μm or more, regardless of the size of the solid additive.

The groove 351 can be formed by honing, for example. That is, by reciprocating the grindstone of the honing machine in the direction along the rotation axis a, the plurality of grooves 351 along the rotation axis a can be formed in the inner peripheral surface 311 of the external gear 3.

In the example of fig. 5, the groove 351 is formed on the inner peripheral surface 311 of the external gear 3, but the groove 351 may be formed on the outer peripheral surface 424 of the bearing 42 instead. The groove 351 may be provided on both the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42. In other words, the groove 351 is preferably provided along the rotation axis a on at least one of the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42.

Fig. 6 is an explanatory diagram showing another example of the groove formation of the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42 of the wave generator 4. In this example, in addition to the groove 351 provided on the inner peripheral surface 311 of the external gear 3, another groove 451 is provided on the outer peripheral surface 424 of the bearing 42. The grooves 451 are provided across both ends of the outer peripheral surface 424 of the bearing 42 along the rotation axis a. In addition, the groove 451 is provided in plural. These grooves 451 are also referred to as "second grooves 451" or "other grooves 451". Preferable values of the direction, depth, and width of the second groove 451 are the same as those of the first groove 351 described above. Further, the second groove 451 preferably intersects the first groove 351. The reason is that when the first groove 351 and the second groove 451 are parallel to each other, both may become rotational resistance. The angle θ formed by the first groove 351 and the second groove 451 is preferably 10 degrees or less, and more preferably 5 degrees or less.

The second groove 451 may be formed on the same surface as the first groove 351. Specifically, when the first groove 351 is formed in the inner peripheral surface 311 of the external gear 3, the second groove 451 may also be formed in the inner peripheral surface 311 of the external gear 3. In addition, when the first groove 351 is formed in the outer circumferential surface 424 of the bearing 42, the second groove 451 may also be formed in the outer circumferential surface 424 of the bearing 42. However, as in the example of fig. 6, it is preferable that one of the

grooves

351, 451 be formed in one of the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42, and the other of the

grooves

351, 451 be formed in the other of the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42.

As described above, in the above-described embodiment, the groove 351 is provided along the rotation axis a in at least one of the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42. As a result, even if the outer peripheral surface 424 of the bearing 42 rotates relative to the external gear 3 with the rotation of the wave generator 4, the grease GR between the inner peripheral surface 311 of the external gear 3 and the outer peripheral surface 424 of the bearing 42 can be easily held by the grooves 351 along the rotation axis a.

In the above-described embodiment, the cup-type externally toothed gear 3 is used, but instead, a cap-type externally toothed gear may be used. In the gear device having the cap-type external gear, the grooves described above with reference to fig. 5 and 6 can be applied, and thus the same effects as those described above can be obtained.

The present disclosure is not limited to the above-described embodiments, and can be implemented in various ways within a scope not departing from the gist thereof. For example, the present disclosure can also be realized by the following manner (aspect). Technical features in the above-described embodiments corresponding to technical features in the respective embodiments described below may be appropriately replaced or combined in order to solve part or all of the technical problems of the present disclosure or achieve part or all of the effects of the present disclosure. Note that, if this technical feature is not described as essential in the present specification, it can be deleted as appropriate.

(1) According to a first aspect of the present disclosure, a gear device is provided. The gear device is provided with: an internal gear; an external gear having flexibility, the external gear partially meshing with the internal gear and relatively rotating around a rotation axis with respect to the internal gear; and a wave generator that contacts an inner peripheral surface of the external gear and moves a meshing position of the internal gear and the external gear in a circumferential direction around the rotation shaft. The wave generator has a cam having an outer peripheral surface with an elliptical shape, and a bearing disposed between the inner peripheral surface of the external gear and the outer peripheral surface of the cam. The inner peripheral surface of the external gear is coated with grease, and a groove is provided along the rotating shaft in at least one of the inner peripheral surface of the external gear and the outer peripheral surface of the bearing.

According to this gear device, even if the outer peripheral surface of the bearing rotates relative to the external gear with the rotation of the wave generator, the grease between the inner peripheral surface of the external gear and the outer peripheral surface of the bearing can be easily retained by the groove along the rotation shaft. As a result, the wave generator can be smoothly rotated.

(2) In the above gear device, an angle formed by the groove and the rotation axis may be 5 degrees or less.

According to this gear device, since the groove extends in a direction substantially parallel to the rotation axis, grease can be easily guided between the external gear and the internal gear.

(3) In the gear device, both end portions of the external gear along the rotation shaft may have a first end portion that is open and a second end portion that is opposite to the first end portion, the wave generator may be fitted into the inner peripheral surface of the external gear at a position closer to the first end portion than to the second end portion of the external gear, the groove may be provided in the inner peripheral surface of the external gear, and the groove may extend from the first end portion to the second end portion and may be provided over a portion of the inner peripheral surface of the external gear that is in contact with the bearing of the wave generator.

According to this gear device, since the groove is provided over a portion of the inner peripheral surface of the external gear that is in contact with the bearing of the wave generator, grease can be easily held between the external gear and the bearing of the wave generator. Further, since the groove extends from the first end portion to the second end portion of the opening of the external gear, the grease can be easily guided between the external gear and the internal gear via the first end portion.

(4) In the above gear device, the groove may be provided on the outer peripheral surface of the bearing, and the groove may be provided along the rotation shaft across both ends of the outer peripheral surface of the bearing.

According to this gear device, since the grooves are provided across both ends of the outer peripheral surface of the bearing of the wave generator, grease can be easily held between the externally toothed gear and the bearing of the wave generator.

(5) In the above gear device, a plurality of the grooves may be provided.

According to this gear device, sufficient grease can be easily held between the external gear and the bearing of the wave generator.

(6) In the above gear device, at least one of the inner peripheral surface of the external gear and the outer peripheral surface of the bearing may be provided with another groove intersecting the groove.

According to this gear device, since the intersecting grooves are provided, grease can be retained by both of the intersecting grooves.

(7) According to a second aspect of the present disclosure, a robot is provided. The robot includes: a first member constituting a base or an arm; a second member that constitutes an arm portion and is provided to be rotatable with respect to the first member; and a gear device that transmits a driving force from one side to the other side of the first member and the second member. The gear device is provided with: an internal gear; an external gear having flexibility, the external gear partially meshing with the internal gear and relatively rotating around a rotation axis with respect to the internal gear; and a wave generator that contacts an inner peripheral surface of the external gear and moves a meshing position of the internal gear and the external gear in a circumferential direction around the rotation shaft. The wave generator has a cam having an outer peripheral surface with an elliptical shape, and a bearing disposed between the inner peripheral surface of the external gear and the outer peripheral surface of the cam. The inner peripheral surface of the external gear is coated with grease, and a groove is provided along the rotating shaft in at least one of the inner peripheral surface of the external gear and the outer peripheral surface of the bearing.

According to this robot, even if the outer peripheral surface of the bearing rotates relative to the external gear with the rotation of the wave generator, the grease between the inner peripheral surface of the external gear and the outer peripheral surface of the bearing can be easily retained by the groove along the rotation shaft. As a result, the wave generator can be smoothly rotated.

Claims

1. A gear device is characterized by comprising:

an internal gear;

an external gear having flexibility, the external gear partially meshing with the internal gear and relatively rotating around a rotation axis with respect to the internal gear; and

a wave generator that contacts an inner peripheral surface of the external gear and moves a meshing position of the internal gear and the external gear in a circumferential direction around the rotation shaft,

the wave generator has a cam having an outer peripheral surface of an elliptical shape, and a bearing disposed between the inner peripheral surface of the external gear and the outer peripheral surface of the cam,

the inner peripheral surface of the external gear is coated with grease,

a groove is provided along the rotating shaft in at least one of the inner peripheral surface of the external gear and the outer peripheral surface of the bearing.

2. The gear arrangement according to claim 1,

the angle formed by the groove and the rotating shaft is less than or equal to 5 degrees.

3. Gear unit according to claim 1 or 2,

both end portions of the external gear along the rotation shaft have a first end portion that is open and a second end portion on the opposite side of the first end portion,

the wave generator is embedded in the inner peripheral surface of the external gear at a position closer to the first end portion than to the second end portion of the external gear,

the groove is provided on the inner peripheral surface of the external gear,

the groove extends from the first end portion to the second end portion, and is provided over a portion of the inner peripheral surface of the external gear that is in contact with the bearing of the wave generator.

4. Gear unit according to claim 1 or 2,

the groove is provided on the outer peripheral surface of the bearing,

the grooves are provided across both ends of the outer peripheral surface of the bearing along the rotation shaft.

5. The gear arrangement according to claim 1,

the groove is provided in plurality.

6. The gear arrangement according to claim 1,

at least one of the inner peripheral surface of the external gear and the outer peripheral surface of the bearing is provided with another groove intersecting the groove.

7. A robot is characterized by comprising:

a first member constituting a base or an arm;

a second member that constitutes an arm portion and is provided to be rotatable with respect to the first member; and

a gear device for transmitting a driving force from one side to the other side of the first member and the second member,

the gear device is provided with:

an internal gear;

the inner peripheral surface of the external gear is coated with grease,